Method for transmitting downlink feedback information, base station, and terminal device

ABSTRACT

The present disclosure discloses a method for transmitting downlink feedback information, a base station, and a terminal device, so as to ensure that the base station correctly receives the downlink feedback information sent by the terminal device, thereby effectively improving a transmission success rate of the downlink feedback information. In embodiments of the present disclosure, the method includes: sending, by the base station, indication information to the terminal device, where the indication information is used to indicate a target time-frequency resource location, the target time-frequency resource location is a time-frequency resource location at which the terminal device sends the downlink feedback information, and the downlink feedback information is used to feed back a reception status of downlink data that should be received by the terminal device; and receiving, by the base station, the downlink feedback information sent by the terminal device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2015/100212, filed on Dec. 31, 2015, the disclosure of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the field of communicationstechnologies, and in particular, to a method for transmitting downlinkfeedback information, a base station, and a terminal device.

BACKGROUND

With rapid development of machine-to-machine (Full name: Machine toMachine, M2M for short) communications applications, market requirementsand the market scale explosively grow. An M2M communications applicationhas a service requirement different from that of a conventionalcommunications service, such as deep coverage and low power consumption.The following solution is put forward for the service requirement of theM2M communications application: After receiving downlink data sent by abase station on a physical downlink shared channel (Full name: PhysicalDownlink Shared Channel, PDSCH for short), a terminal device needs toprovide feedback for the downlink data. If the terminal devicesuccessfully receives the downlink data, the terminal device feeds backan acknowledgement (Full name: Acknowledgement, ACK for short); or ifthe terminal device fails to receive the downlink data, the terminaldevice feeds back a negative acknowledgement (Full name: NegativeAcknowledgement, NACK for short). For example, a data transmissionprocess may be shown in FIG. 1.

Currently, in the data transmission process in FIG. 1, a time-frequencyresource location of downlink feedback information is mainly mapped byusing a time-frequency resource location of a physical downlink controlchannel (Full name: Physical Downlink Control Channel, PDCCH for short),so that the time-frequency resource location of the downlink feedbackinformation is determined, and the downlink data sent on the PDSCH isfed back at the time-frequency resource location of the downlinkfeedback information.

However, for a system in which cross-PDCCH scheduling is performed, ifthe time-frequency resource location of the downlink feedbackinformation is mapped by using the time-frequency resource location of aPDCCH, a resource conflict may occur because feedback is provided formultiple pieces of the downlink data at a same time-frequency resourcelocation of the downlink feedback information. Consequently, the basestation cannot correctly receive the downlink feedback information sentby a terminal device, and a transmission success rate of the downlinkfeedback information is not high.

SUMMARY

Embodiments of the present disclosure provide a method for transmittingdownlink feedback information, a base station, and a terminal device, soas to ensure that the base station correctly receives the downlinkfeedback information sent by the terminal device, thereby effectivelyimproving a transmission success rate of the downlink feedbackinformation.

In view of this, a first aspect of the present disclosure provides amethod for transmitting downlink feedback information, including:

to avoid a resource conflict caused because feedback is provided formultiple pieces of downlink data at a same time-frequency resourcelocation of the downlink information, sending, by a base station,indication information to a terminal device, where the indicationinformation is used to indicate a target time-frequency resourcelocation, the target time-frequency resource location is atime-frequency resource location at which the terminal device sends thedownlink feedback information, and the downlink feedback information isused to feed back a reception status of downlink data that should bereceived by the terminal device; and

receiving, by the base station, the downlink feedback information sentby the terminal device.

It should be noted that a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

With reference to the first aspect of the present disclosure, in a firstimplementation of the first aspect of the present disclosure, the methodfurther includes:

sending, by the base station, downlink scheduling information to theterminal device; and

after the sending, by a base station, indication information to aterminal device, the method further includes:

sending, by the base station, the downlink data to the terminal deviceaccording to the downlink scheduling information.

It should be noted that the indication information and the downlinkscheduling information are not sent in sequence; that is, the indicationinformation and the downlink scheduling information may be sent in asame message or may be separately sent.

With reference to the first aspect of the present disclosure, in asecond implementation of the first aspect of the present disclosure,

the sending, by a base station, indication information to a terminaldevice includes:

sending, by the base station, on a physical downlink control channelPDCCH, the indication information to the terminal device, where

the PDCCH includes multiple scheduling units, and the indicationinformation alone occupies one scheduling unit on the PDCCH; and thescheduling unit includes information about the time-frequency resourcelocation of the downlink feedback information.

With reference to the first implementation of the first aspect of thepresent disclosure, in a third implementation of the first aspect of thepresent disclosure, the sending, by a base station, indicationinformation to a terminal device includes:

sending, by the base station, on a physical downlink control channelPDCCH, the indication information to the terminal device, where

the PDCCH includes multiple scheduling units, and the indicationinformation shares one scheduling unit with the downlink schedulinginformation.

With reference to the first aspect of the present disclosure, in afourth implementation of the first aspect of the present disclosure,

before the sending, by a base station, indication information to aterminal device, the method includes:

sending, by the base station, downlink scheduling information to theterminal device; and

sending, by the base station, the downlink data to the terminal deviceaccording to the downlink scheduling information.

With reference to the first aspect of the present disclosure, the firstimplementation of the first aspect of the present disclosure, the secondimplementation of the first aspect of the present disclosure, the thirdimplementation of the first aspect of the present disclosure, or thefourth implementation of the first aspect of the present disclosure, ina fifth implementation of the first aspect of the present disclosure,

the receiving, by the base station, the downlink feedback informationsent by the terminal device includes:

receiving, by the base station, the downlink feedback information sentby the terminal device, where the downlink feedback information is asequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

With reference to the first aspect of the present disclosure, the firstimplementation of the first aspect of the present disclosure, the secondimplementation of the first aspect of the present disclosure, the thirdimplementation of the first aspect of the present disclosure, the fourthimplementation of the first aspect of the present disclosure, or thefifth implementation of the first aspect of the present disclosure, in asixth implementation of the first aspect of the present disclosure,

the indication information is further used to indicate a data formatused when the terminal device sends the downlink feedback information;and

the receiving, by the base station, the downlink feedback informationsent by the terminal device includes:

receiving, by the base station, the downlink feedback information thatis sent by the terminal device according to the data format indicated bythe indication information.

In view of this, a second aspect of the present disclosure provides amethod for transmitting downlink feedback information, including:

receiving, by a terminal device, indication information sent by a basestation; and

sending, by the terminal device, at the target time-frequency resourcelocation, the downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information, where the downlink feedback information isused to feed back a reception status of downlink data that should bereceived by the terminal device.

It should be noted that a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

With reference to the second aspect of the present disclosure, in afirst implementation of the second aspect of the present disclosure, themethod further includes:

receiving, by the terminal device, downlink scheduling information sentby the base station; and

after the receiving, by a terminal device, indication information sentby a base station, the method further includes:

receiving, by the terminal device, the downlink data sent by the basestation, where the downlink data is downlink data that is sent by thebase station to the terminal device according to the downlink schedulinginformation.

With reference to the second aspect of the present disclosure, in asecond implementation of the second aspect of the present disclosure,

before the receiving, by a terminal device, indication information sentby a base station, the method further includes:

receiving, by the terminal device, downlink scheduling information sentby the base station; and

receiving, by the terminal device, the downlink data sent by the basestation, where the downlink data is downlink data that is sent by thebase station to the terminal device according to the downlink schedulinginformation.

With reference to the second aspect of the present disclosure, the firstimplementation of the second aspect of the present disclosure, or thesecond implementation of the second aspect of the present disclosure, ina third implementation of the second aspect of the present disclosure,

the sending, by the terminal device, at the target time-frequencyresource location, the downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information includes:

sending, by the terminal device, at the target time-frequency resourcelocation, the downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information, where the downlink feedback information is asequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

With reference to the second aspect of the present disclosure, the firstimplementation of the second aspect of the present disclosure, thesecond implementation of the second aspect of the present disclosure, orthe third implementation of the second aspect of the present disclosure,in a fourth implementation of the second aspect of the presentdisclosure,

the indication information is further used to indicate a data formatused when the terminal device sends the downlink feedback information;and

the sending, by the terminal device, at the target time-frequencyresource location, the downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information includes:

sending, by the terminal device, at the target time-frequency resourcelocation, the downlink feedback information to the base stationaccording to the target time-frequency resource location and the dataformat that are indicated by the indication information.

In view of this, a third aspect of the present disclosure provides abase station, including:

a sending unit, configured to send indication information to a terminaldevice, where the indication information is used to indicate a targettime-frequency resource location, the target time-frequency resourcelocation is a time-frequency resource location at which the terminaldevice sends downlink feedback information, and the downlink feedbackinformation is used to feed back a reception status of downlink datathat should be received by the terminal device; and

a receiving unit, configured to receive the downlink feedbackinformation sent by the terminal device.

With reference to the third aspect of the present disclosure, in a firstimplementation of the third aspect of the present disclosure,

the sending unit is further configured to send downlink schedulinginformation to the terminal device; and

after the sending unit sends the indication information to the terminaldevice, the sending unit is further configured to send the downlink datato the terminal device according to the downlink scheduling information.

With reference to the third aspect of the present disclosure, in asecond implementation of the third aspect of the present disclosure,

the sending unit is specifically configured to send, on a physicaldownlink control channel PDCCH, the indication information to theterminal device, where

the PDCCH includes multiple scheduling units, and the indicationinformation alone occupies one scheduling unit on the PDCCH.

With reference to the first implementation of the third aspect of thepresent disclosure, in a third implementation of the third aspect of thepresent disclosure,

the sending unit is specifically configured to send, on a physicaldownlink control channel PDCCH, the indication information to theterminal device, where

the PDCCH includes multiple scheduling units, and the indicationinformation shares one scheduling unit with the downlink schedulinginformation.

With reference to the third aspect of the present disclosure, in afourth implementation of the third aspect of the present disclosure,

the sending unit is further configured to: send downlink schedulinginformation to the terminal device; and send the downlink data to theterminal device according to the downlink scheduling information.

With reference to the third aspect of the present disclosure, the firstimplementation of the third aspect of the present disclosure, the secondimplementation of the third aspect of the present disclosure, the thirdimplementation of the third aspect of the present disclosure, or thefourth implementation of the third aspect of the present disclosure, ina fifth implementation of the third aspect of the present disclosure,

the receiving unit is specifically configured to receive the downlinkfeedback information sent by the terminal device, where the downlinkfeedback information is a sequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

With reference to the third aspect of the present disclosure, the firstimplementation of the third aspect of the present disclosure, the secondimplementation of the third aspect of the present disclosure, the thirdimplementation of the third aspect of the present disclosure, the fourthimplementation of the third aspect of the present disclosure, or thefifth implementation of the third aspect of the present disclosure, in asixth implementation of the third aspect of the present disclosure,

the indication information is further used to indicate a data formatused when the terminal device sends the downlink feedback information;and

the receiving unit is specifically configured to receive the downlinkfeedback information that is sent by the terminal device according tothe data format indicated by the indication information.

In view of this, a fourth aspect of the present disclosure provides aterminal device, including:

a receiving unit, configured to receive indication information sent by abase station; and

a sending unit, configured to send, at the target time-frequencyresource location, downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information, where the downlink feedback information isused to feed back a reception status of downlink data that should bereceived by the terminal device.

With reference to the fourth aspect of the present disclosure, in afirst implementation of the fourth aspect of the present disclosure,

the receiving unit is further configured to receive downlink schedulinginformation sent by the base station; and

after the receiving unit receives the indication information sent by thebase station, the receiving unit is further configured to receive thedownlink data sent by the base station, where the downlink data isdownlink data that is sent by the base station to the terminal deviceaccording to the downlink scheduling information.

With reference to the fourth aspect of the present disclosure, in asecond implementation of the fourth aspect of the present disclosure,

before the receiving unit receives the indication information sent bythe base station, the receiving unit is further configured to: receivedownlink scheduling information sent by the base station; and receivethe downlink data sent by the base station, where the downlink data isdownlink data that is sent by the base station to the terminal deviceaccording to the downlink scheduling information.

With reference to the fourth aspect of the present disclosure, the firstimplementation of the fourth aspect of the present disclosure, or thesecond implementation of the fourth aspect of the present disclosure, ina third implementation of the fourth aspect of the present disclosure,

the sending unit is specifically configured to send, at the targettime-frequency resource location, the downlink feedback information tothe base station according to the target time-frequency resourcelocation indicated by the indication information, where the downlinkfeedback information is a sequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

With reference to the fourth aspect of the present disclosure, the firstimplementation of the fourth aspect of the present disclosure, thesecond implementation of the fourth aspect of the present disclosure, orthe third implementation of the fourth aspect of the present disclosure,in a fourth implementation of the fourth aspect of the presentdisclosure,

the indication information is further used to indicate a data formatused when the terminal device sends the downlink feedback information;and

the sending unit is specifically configured to send, at the targettime-frequency resource location, the downlink feedback information tothe base station according to the target time-frequency resourcelocation and the data format that are indicated by the indicationinformation.

Compared with the prior art, in the present disclosure, a time-frequencyresource location at which a terminal device sends downlink feedbackinformation is indicated by a base station by using indicationinformation, and the base station can ensure, by using the indicationinformation, that time-frequency resource locations of downlink feedbackinformation of different downlink data are different, so as to avoid aresource conflict problem in the prior art. Therefore, in the presentdisclosure, it can be ensured that the base station correctly receivesthe downlink feedback information sent by the terminal device, therebyeffectively improving a transmission success rate of the downlinkfeedback information.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly describes theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showmerely some embodiments of the present disclosure, or persons ofordinary skill in the art may still derive other drawings from theseaccompanying drawings without creative efforts.

FIG. 1 is an existing transmission flowchart of downlink feedbackinformation;

FIG. 2 is a flowchart of a method for transmitting downlink feedbackinformation according to an embodiment of the present disclosure;

FIG. 3 is another flowchart of a method for transmitting downlinkfeedback information according to an embodiment of the presentdisclosure;

FIG. 4 is an interaction flowchart of a method for transmitting downlinkfeedback information according to an embodiment of the presentdisclosure;

FIG. 5 is another interaction flowchart of a method for transmittingdownlink feedback information according to an embodiment of the presentdisclosure;

FIG. 6 is another interaction flowchart of a method for transmittingdownlink feedback information according to an embodiment of the presentdisclosure;

FIG. 7 is a schematic structural diagram of a base station according toan embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of a terminal device accordingto an embodiment of the present disclosure; and

FIG. 9 is a schematic structural diagram of a server according to anembodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure provide a method for transmittingdownlink feedback information, a base station, and a terminal device, soas to resolve a problem of feedback information resource selection in acommunications system in which cross-PDCCH scheduling is performed.

To make persons skilled in the art understand the technical solutions inthe present disclosure better, the following clearly describes thetechnical solutions in the embodiments of the present disclosure withreference to the accompanying drawings in the embodiments of the presentdisclosure. Apparently, the described embodiments are merely some ratherthan all of the embodiments of the present disclosure. All otherembodiments obtained by persons of ordinary skill in the art based onthe embodiments of the present disclosure without creative efforts shallfall within the protection scope of the present disclosure.

In the specification, claims, and accompanying drawings of the presentdisclosure, the terms “first”, “second”, “third”, “fourth”, and so on(if existent) are intended to distinguish between similar objects but donot necessarily indicate a specific order or sequence. It should beunderstood that the data termed in such a way are interchangeable inproper circumstances so that the embodiments of the present disclosuredescribed herein can be implemented in other orders than the orderillustrated or described herein. In addition, the terms “include”,“contain” and any other variants mean to cover the non-exclusiveinclusion. For example, a process, method, system, product, or devicethat includes a list of steps or units is not necessarily limited tothose units, but may include other units not expressly listed orinherent to such a process, method, system, product, or device.

Although an LTE system is used as an example for description in theforegoing background part, persons skilled in the art should know thatthe present disclosure not only applies to the LTE system, but alsoapplies to other wireless communications systems, such as Global Systemfor Mobile communications (Global System for Mobile Communication, GSM),a Universal Mobile Telecommunications System (Universal MobileTelecommunications System, UMTS), a Code Division Multiple Access (CodeDivision Multiple Access, CDMA) system, and a new network system. Thefollowing describes specific embodiments by using the LTE system as anexample.

A terminal device related to an embodiment of the present disclosure mayrefer to a device that provides a user with voice and/or dataconnectivity, a handheld device that has a wireless connection function,or another processing device connected to a wireless modem. The wirelessterminal may communicate with one or more core networks by using a radioaccess network (Radio Access Network, RAN). The wireless terminal may bea mobile terminal such as a mobile phone (or referred to as a “cellular”phone), or a computer having a mobile terminal function. For example,the wireless terminal may be a portable, pocket-sized, handheld,computer built-in, or in-vehicle mobile apparatus, which exchanges voiceand/or data with the radio access network. For example, the wirelessterminal may be a device, such as a personal communications service(PCS, Personal Communication Service) phone, a cordless phone, a SessionInitiation Protocol (SIP) phone, a wireless local loop (WLL, WirelessLocal Loop) station, or a personal digital assistant (PDA, PersonalDigital Assistant). The wireless terminal may also be referred to as asystem, a subscriber unit (Subscriber Unit), a subscriber station(Subscriber Station), a mobile station (Mobile Station), a mobile(Mobile) terminal, a remote station (Remote Station), an access point(Access Point), a remote terminal (Remote Terminal), an access terminal(Access Terminal), a user terminal (User Terminal), a user agent (UserAgent), a user device (User Device), or user equipment (User Equipment).

A base station related to this embodiment of the present disclosure maybe configured to perform conversion between a received over-the-airframe and an IP packet, and serve as a router between the wirelessterminal and the rest of an access network. The rest of the accessnetwork may include an Internet Protocol (IP) network. The base stationmay be further configured to coordinate attribute management of an airinterface. For example, the base station may be a base transceiverstation (BTS, Base Transceiver Station) in GSM or CDMA, may be a NodeB(NodeB) in WCDMA, or may be an evolved NodeB (eNB or e-NodeB,evolutional Node B) in LTE. This is not limited in this application.

The following describes a method for transmitting downlink feedbackinformation in the present disclosure with reference to specificembodiments.

Referring to FIG. 2, an embodiment of the method for transmittingdownlink feedback information in an embodiment of the present disclosureincludes the following steps.

101. A base station sends indication information to a terminal device,where the indication information is used to indicate a targettime-frequency resource location, the target time-frequency resourcelocation is a time-frequency resource location at which the terminaldevice sends downlink feedback information, and the downlink feedbackinformation is used to feed back a reception status of downlink datathat should be received by the terminal device.

In this embodiment, the base station may send, on a PDCCH, theindication information to the terminal device, or the base station maysend, on a PDSCH, the indication information to the terminal device.

It should be noted that the downlink data is downlink data that is sentby the base station to the terminal device in advance, and a time atwhich the base station sends the downlink data to the terminal device inadvance may be before step 101, may be after step 101, or, if possible,may be the same as a time at which step 101 is performed. In addition,the foregoing reception status indicates whether the terminal devicecorrectly receives the downlink data, and the time-frequency resourcelocation includes a time location and/or a frequency location.

It should be noted that, in some embodiments of the present disclosure,the sending, by a base station, indication information to a terminaldevice includes:

sending, by the base station, on the PDCCH, the indication informationto the terminal device, where the PDCCH includes multiple schedulingunits, and the indication information alone occupies one schedulingunit.

It should be noted that the indication information that alone occupiesone scheduling unit on the PDCCH may be downlink control information(Full name: Downlink Control Information, DCI for short). An examplescheduling unit may include information about the time-frequencyresource location, a modulation and coding scheme (Full name: Modulationand Coding Scheme, MCS for short), a code block size (Full name: CodeBlock Size), and a message identifier (Full name: Message Identifier,MID for short), and may further include other information, which is notlisted herein. The information about the time-frequency resourcelocation is used to indicate a time location and/or a frequency locationat which a user sends the downlink feedback information. Informationthat indicates the time location and information that indicates thefrequency location may be separately indicated, or may be indicatedtogether. The MCS indication information and the CBS indicationinformation are used to indicate a data format used when the user sendsthe downlink feedback information. For example, if the downlink feedbackinformation needs to be processed by means of coding, modulation, andthe like, the MCS information may be used to indicate a bit rate and amodulation scheme that are of the downlink feedback information, and theCBS indication information may be used to indicate a packet size of thedownlink feedback information. In addition, if a form of the downlinkfeedback information is a sequence, the CBS indication information maybe used to indicate a sequence length of the downlink feedbackinformation. The message identifier may be used to identify a specifictype of scheduling information to which the indication informationbelongs, such as PDSCH scheduling information, PUSCH schedulinginformation, or feedback information scheduling information.

102. The base station receives the downlink feedback information sent bythe terminal device.

After the base station sends the indication information to the terminaldevice, the base station receives the downlink feedback information sentby the terminal device.

Optionally, in some embodiments of the present disclosure, thereceiving, by the base station, the downlink feedback information sentby the terminal device may be specifically as follows:

receiving, by the base station, the downlink feedback information sentby the terminal device, where the downlink feedback information is asequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

For example, two sequences in a sequence group that are cross-correlatedare a pseudo-random sequence 1 and a pseudo-random sequence 2, and twosequences in a sequence group that are orthogonal to each other are aHadamard sequence 1×a Hadamard sequence 2. Another combination isfurther included, and details are not described herein.

In this embodiment, a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

The foregoing has described the technical solutions in the presentdisclosure from a perspective of the base station. The followingdescribes a technical solution in the present disclosure from aperspective of the terminal device.

Referring to FIG. 3, another embodiment of a method for transmittingdownlink feedback information in an embodiment of the present disclosureincludes the following steps.

201. A terminal device receives indication information sent by a basestation.

In this embodiment, the terminal device may receive, on a PDCCH, theindication information sent by the base station, or the terminal devicemay receive, on a PDSCH, the indication information sent by the basestation.

202. The terminal device sends, at the target time-frequency resourcelocation, downlink feedback information to the base station according tothe target time-frequency resource location indicated by the indicationinformation, where the downlink feedback information is used to feedback a reception status of downlink data that should be received by theterminal device.

After the terminal device receives the indication information sent bythe base station, the terminal device sends, at the targettime-frequency resource location, the downlink feedback information tothe base station according to the target time-frequency resourcelocation indicated by the indication information. The downlink feedbackinformation is feedback information of the downlink data that should bereceived by the terminal device.

It should be noted that the downlink data is downlink data that is sentby the base station to the terminal device in advance, and a time atwhich the base station sends the downlink data to the terminal device inadvance may be before step 201, may be after step 201, or, if possible,may be the same as a time at which step 201 is performed. In addition,the foregoing reception status indicates whether the terminal devicecorrectly receives the downlink data.

In this embodiment, a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

The foregoing has described the technical solutions in the presentdisclosure from the perspectives of the base station and the terminaldevice. The following describes in detail a technical solution in thepresent disclosure from a perspective of interaction between the basestation and the terminal device.

Referring to FIG. 4, another embodiment of a method for transmittingdownlink feedback information in an embodiment of the present disclosureincludes the following steps.

301. A base station sends downlink scheduling information to a terminaldevice.

In this embodiment, to send downlink data to the terminal device, thebase station needs to first send the downlink scheduling information tothe terminal device.

302. The base station sends downlink data to the terminal device.

After the base station sends the downlink scheduling information to theterminal device, the base station sends the downlink data to theterminal device according to an indication of the downlink schedulinginformation.

303. The base station sends indication information to the terminaldevice.

After the base station sends the downlink data to the terminal device,the base station sends the indication information to the terminaldevice. The indication information is used to indicate a targettime-frequency resource location, the target time-frequency resourcelocation is a time-frequency resource location at which the terminaldevice sends the downlink feedback information, and the downlinkfeedback information is used to feed back a reception status of thedownlink data that should be received by the terminal device.

304. The terminal device sends downlink feedback information to the basestation.

After the base station sends the indication information to the terminaldevice, the terminal device sends, at the target time-frequency resourcelocation, the downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information. The downlink feedback information iscorresponding to the downlink data that should be received by theterminal device.

It should be noted that the indication information may be further usedto indicate a data format used when the terminal device sends thedownlink feedback information. Therefore, in some embodiments of thepresent disclosure, the sending, by the terminal device, downlinkfeedback information to the base station may be further specifically asfollows: sending, by the terminal device, at the target time-frequencyresource location, in the data format, the downlink feedback informationto the base station according to the target time-frequency resourcelocation and the data format that are indicated by the indicationinformation.

In addition, the indication information may be used to indicate otherinformation, which is not listed herein.

It should be noted that, in some embodiments of the present disclosure,the indication information and the downlink scheduling information arenot sent in sequence; that is, the indication information and thedownlink scheduling information may be sent in a same message or may beseparately sent.

In this embodiment, a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

In addition, in this embodiment, indication information is sent to aterminal device after sending of downlink data is complete. Therefore, aprocess of supporting the technical solutions in the present disclosureis provided, thereby enriching the technical solutions in the presentdisclosure.

Referring to FIG. 5, another embodiment of a method for transmittingdownlink feedback information in an embodiment of the present disclosureincludes the following steps.

401. A base station sends downlink scheduling information and indicationinformation to a terminal device.

In this embodiment, the base station sends, on a PDCCH, the downlinkscheduling information and the indication information to the terminaldevice. The PDCCH includes multiple scheduling units, and the indicationinformation shares one scheduling unit with the downlink schedulinginformation. In addition, that the indication information shares onescheduling unit with the downlink scheduling information may be: Theindication information is included in the downlink schedulinginformation.

It should be noted that the indication information may be placed in anyPDCCH period for transmission. The base station may place the downlinkscheduling information and the indication information in a samescheduling period, so that the terminal device may simultaneouslyobtain, in the scheduling period, the downlink scheduling informationand the indication information. Certainly, if a scheduling resource in ascheduling period in which the downlink scheduling information islocated is limited, the base station may alternatively place theindication information in another scheduling period. For example, theindication information is placed in a scheduling period before or afterthe scheduling period in which the downlink scheduling information islocated.

402. The base station sends downlink data to the terminal device.

After the base station sends the downlink scheduling information to theterminal device, the base station sends the downlink data to theterminal device according to an indication of the downlink schedulinginformation.

403. The terminal device sends downlink feedback information to the basestation.

After the terminal device receives the indication information, theterminal device sends, at a target time-frequency resource location, thedownlink feedback information to the base station according to thetarget time-frequency resource location indicated by the indicationinformation. The downlink feedback information is used to feed back areception status of the downlink data that should be received by theterminal device.

It should be noted that the indication information may be further usedto indicate a data format used when the terminal device sends thedownlink feedback information. Therefore, in some embodiments of thepresent disclosure, the sending, by the terminal device, downlinkfeedback information to the base station may be further specifically asfollows: sending, by the terminal device, at the target time-frequencyresource location, in the data format, the downlink feedback informationto the base station according to the target time-frequency resourcelocation and the data format that are indicated by the indicationinformation.

In addition, the indication information may be used to indicate otherinformation, which is not listed herein.

In this embodiment, a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

In addition, in this embodiment, indication information is sent by abase station together with downlink scheduling information. Therefore, aprocess of supporting the technical solutions in the present disclosureis provided, thereby enriching the technical solutions in the presentdisclosure.

Referring to FIG. 6, another embodiment of a method for transmittingdownlink feedback information in an embodiment of the present disclosureincludes the following steps.

501. A base station sends downlink scheduling information to a terminaldevice.

In this embodiment, the base station sends, on a PDCCH, the downlinkscheduling information to the terminal device.

502. The base station sends downlink data to the terminal device, wherethe downlink data carries indication information.

The base station sends, on a PDSCH, the downlink data to the terminaldevice according to an indication of the downlink schedulinginformation. The downlink data carries the indication information.

503. The terminal device sends downlink feedback information to the basestation.

After the terminal device receives the indication information, theterminal device sends, at a target time-frequency resource location, thedownlink feedback information to the base station according to thetarget time-frequency resource location indicated by the indicationinformation. The downlink feedback information is used to feed back areception status of the downlink data that should be received by theterminal device.

It should be noted that the indication information may be further usedto indicate a data format used when the terminal device sends thedownlink feedback information. Therefore, in some embodiments of thepresent disclosure, the sending, by the terminal device, downlinkfeedback information to the base station may be further specifically asfollows: sending, by the terminal device, at the target time-frequencyresource location, in the data format, the downlink feedback informationto the base station according to the target time-frequency resourcelocation and the data format that are indicated by the indicationinformation.

In addition, the indication information may be used to indicate otherinformation, which is not listed herein.

In this embodiment, a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

In addition, in this embodiment, indication information is sent by abase station together with downlink data. Therefore, a process ofsupporting the technical solutions in the present disclosure isprovided, thereby enriching the technical solutions in the presentdisclosure.

For ease of understanding, the following describes, by using an actualapplication scenario, the method for transmitting downlink feedbackinformation in this embodiment of the present disclosure.

A base station sends, on a PDCCH, downlink scheduling information to aterminal device. The base station sends downlink data to the terminaldevice according to an indication of the downlink schedulinginformation. After the base station sends the downlink data to theterminal device, the base station sends indication information to theterminal device. The indication information alone occupies onescheduling unit, the scheduling unit includes information about atime-frequency resource location, MCS information, and CBS information,and the MCS information and the CBS information are used to indicate adata format used when the terminal device sends the downlink feedbackinformation. After receiving the indication information, the terminaldevice parses the indication information, and feeds back the downlinkfeedback information to the base station according to the time-frequencyresource location and the data format that are indicated by theindication information.

In the foregoing embodiments, the base station indicates in real time atime-frequency resource location and a sending format that are of thedownlink feedback information. In addition, a scheme of fixed resourcemapping may be used. Specifically:

In the downlink feedback information sent by the terminal device, asignal form may be a sequence. Therefore, an ACK and a NACK may beseparately represented by using different sequences. If the terminaldevice successfully receives the downlink data, the terminal deviceneeds to feed back the ACK, that is, the terminal device sends asequence that represents the ACK; or if the terminal device fails toreceive the downlink data, the terminal device needs to feed back theNACK, that is, the terminal device sends a sequence that represents theNACK. In addition, the sequence that represents the ACK and the sequencethat represents the NACK should be cross-correlated and/or orthogonal toeach other, such as a pseudo-random sequence, a Hadamard sequence, or aproduct sequence of a pseudo-random sequence and a Hadamard sequence.

For determining of the time-frequency resource location, after receivingthe downlink data, the terminal device determines, according to an endmoment of the downlink data, an available feedback information resourceblock that is closest in time, and then determines the time-frequencyresource location of the downlink feedback information according to astart control channel element (Control Channel Element, CCE) resourcelocation of scheduling information of the downlink data.

For determining of the downlink feedback information, sequences used forrepresenting the ACK and the NACK fed back by the terminal device arerelated to a start frame number of a scheduling period in which thedownlink scheduling information of the downlink data of the terminaldevice is located. For the downlink data scheduled in differentscheduling periods, sequences used for representing the ACK and the NACKfed back are different, and are cross-correlated or orthogonal to eachother.

Generally, the terminal device determines the time-frequency location ofthe downlink feedback information according to the end moment of thedownlink data, or the terminal device determines the time-frequencylocation of the downlink feedback information according to the endmoment of the downlink data and the start CCE resource location ofdownlink control information (Downlink Control Information, DCI) of thescheduled downlink data, and selects, according to the start framenumber of the scheduling period in which the DCI of the scheduleddownlink data is located, different sequences to represent the ACK andthe NACK.

In the foregoing scheme of fixed resource mapping, code divisionprocessing is performed, based on different DCI periods, on sequencesthat represent an ACK and a NACK. Even if downlink feedback informationthat is of a terminal device and that is in different DCI periodscollides, because of code division, no interference will occur, therebyensuring that the downlink feedback information is correctly received.

The following describes a base station in an embodiment of the presentdisclosure. Referring to FIG. 7, an embodiment of the base station in anembodiment of the present disclosure includes:

a sending unit 601, configured to send indication information to aterminal device, where the indication information is used to indicate atarget time-frequency resource location, the target time-frequencyresource location is a time-frequency resource location at which theterminal device sends downlink feedback information, and the downlinkfeedback information is used to feed back a reception status of downlinkdata that should be received by the terminal device; and

a receiving unit 602, configured to receive the downlink feedbackinformation sent by the terminal device.

In this embodiment, a time-frequency resource location at which aterminal device sends downlink feedback information is indicated by asending unit 601 by using indication information, and the sending unit601 can ensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that a base station correctly receives the downlink feedbackinformation sent by the terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

Optionally, in some embodiments of the present disclosure, the sendingunit 601 is further configured to: send downlink scheduling informationto the terminal device; and send the downlink data to the terminaldevice according to the downlink scheduling information. Further, insome embodiments of the present disclosure, the sending unit 601 isspecifically configured to send, on a physical downlink control channelPDCCH, the indication information to the terminal device. The PDCCHincludes multiple scheduling units, and the indication information aloneoccupies one scheduling unit on the PDCCH.

Optionally, in some embodiments of the present disclosure, the sendingunit 601 is further configured to send downlink scheduling informationto the terminal device; and after sending the indication information tothe terminal device, the sending unit 601 is further configured to sendthe downlink data to the terminal device according to the downlinkscheduling information. Further, in some embodiments of the presentdisclosure, the sending unit 601 is specifically configured to send, ona physical downlink control channel PDCCH, the indication information tothe terminal device. The PDCCH includes multiple scheduling units, andthe indication information shares one scheduling unit with the downlinkscheduling information. That the indication information shares onescheduling unit with the downlink scheduling information includes: Theindication information is included in the downlink schedulinginformation.

Optionally, in some embodiments of the present disclosure, the receivingunit 602 is specifically configured to receive the downlink feedbackinformation sent by the terminal device, where the downlink feedbackinformation is a sequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

Optionally, in some embodiments of the present disclosure, theindication information is further used to indicate a data format usedwhen the terminal device sends the downlink feedback information, andthe receiving unit 602 is specifically configured to receive thedownlink feedback information that is sent by the terminal deviceaccording to the data format indicated by the indication information.

The following describes a terminal device in the present disclosure.Referring to FIG. 8, an embodiment of the terminal device in anembodiment of the present disclosure includes:

a receiving unit 701, configured to receive indication information sentby a base station; and

a sending unit 702, configured to send, at a target time-frequencyresource location, downlink feedback information to the base stationaccording to the target time-frequency resource location indicated bythe indication information, where the downlink feedback information isused to feed back a reception status of downlink data that should bereceived by the terminal device.

In this embodiment, a time-frequency resource location at which asending unit 702 sends downlink feedback information is indicated by abase station by using indication information, and the base station canensure, by using the indication information, that time-frequencyresource locations of downlink feedback information of differentdownlink data are different, so as to avoid a resource conflict problemin the prior art. Therefore, in the present disclosure, it can beensured that the base station correctly receives the downlink feedbackinformation sent by a terminal device, thereby effectively improving atransmission success rate of the downlink feedback information.

Optionally, in some embodiments of the present disclosure, before thereceiving unit 701 receives the indication information sent by the basestation, the receiving unit 701 is further configured to: receivedownlink scheduling information sent by the base station; and receivethe downlink data sent by the base station. The downlink data isdownlink data that is sent by the base station to the terminal deviceaccording to the downlink scheduling information.

Optionally, in some embodiments of the present disclosure, after thereceiving unit 701 receives the indication information sent by the basestation, the receiving unit 701 is further configured to receive thedownlink data sent by the base station. The downlink data is downlinkdata that is sent by the base station to the terminal device accordingto downlink scheduling information.

It should be noted that, in some embodiments of the present disclosure,the indication information and the downlink scheduling information arenot sent in sequence; that is, the indication information and thedownlink scheduling information may be sent in a same message or may beseparately sent.

Optionally, in some embodiments of the present disclosure, the sendingunit 702 is specifically configured to send, at the targettime-frequency resource location, the downlink feedback information tothe base station according to the target time-frequency resourcelocation indicated by the indication information, where the downlinkfeedback information is a sequence; and

the downlink feedback information represents an acknowledgement ACK or anegative acknowledgement NACK separately by using different sequences,and a sequence that represents the ACK and a sequence that representsthe NACK are cross-correlated and/or orthogonal to each other.

Optionally, in some embodiments of the present disclosure, theindication information is further used to indicate a data format usedwhen the terminal device sends the downlink feedback information, andthe sending unit 702 is specifically configured to send, at the targettime-frequency resource location, in the data format, the downlinkfeedback information to the base station according to the targettime-frequency resource location and the data format that are indicatedby the indication information.

For ease of understanding, the following describes, by using an actualapplication scenario, interaction between the base station and the unitsin the terminal device in the embodiments of the present disclosure.

The sending unit 601 sends, on a PDCCH, downlink scheduling informationto a terminal device, and sends downlink data to the terminal deviceaccording to an indication of the downlink scheduling information. Aftersending the downlink data to the terminal device, the sending unit 601sends indication information to the receiving unit 701. The indicationinformation alone occupies one scheduling unit, the scheduling unitincludes information about a time-frequency resource location, MCSinformation, and CBS information, and the MCS information and the CBSinformation are used to indicate a data format used when the sendingunit 702 sends downlink feedback information. After receiving theindication information, the receiving unit 701 parses the indicationinformation; and the sending unit 702 feeds back the downlink feedbackinformation to the receiving unit 602 according to the time-frequencyresource location and the data format that are indicated by theindication information.

An embodiment of the present disclosure further provides a server.Referring to FIG. 9, an embodiment of the server in an embodiment of thepresent disclosure includes:

FIG. 9 is a schematic structural diagram of the server according to thisembodiment of the present disclosure. The server 800 may have arelatively big difference because of a difference in configuration orperformance, and may include one or more central processing units(central processing units, CPU) 801 (for example, one or moreprocessors), and one or more storage media 804 (for example, one or moremass storage devices) that store an application program 802 or data 803.The storage medium 804 may be a transient storage or a persistentstorage. A program stored in the storage medium 804 may include one ormore modules (not shown in FIG. 9), and each module may include a seriesof instruction operations to be performed on a switch. Further, thecentral processing unit 801 may be configured to communicate with thestorage medium 804 to perform, on the server 800, a series ofinstruction operations in the storage medium 804.

The server 800 may further include one or more power supplies 805, oneor more wired or wireless network interfaces 806, one or moreinput/output interfaces 807, and/or one or more operating systems 808,such as Windows Server, Mac OS X, Unix, Linux, or FreeBSD.

In the foregoing embodiment, the steps performed by the base station maybe based on the server structure shown in FIG. 9.

The foregoing embodiments are merely intended for describing thetechnical solutions of the present disclosure, but not for limiting thepresent disclosure. Although the present disclosure is described indetail with reference to the foregoing embodiments, persons of ordinaryskill in the art should understand that they may still makemodifications to the technical solutions described in the foregoingembodiments or make equivalent replacements to some technical featuresthereof, without departing from the scope of the technical solutions ofthe embodiments of the present disclosure.

What is claimed is:
 1. A method for receiving downlink feedback information, performed by a base station, comprising: sending single downlink control information (DCI) to a terminal device on a physical downlink control channel (PDCCH), wherein the single DCI includes: downlink scheduling information that schedules downlink data, first information that indicates a time location of a resource for acknowledgement/negative acknowledgement (ACK/NACK) in response to the downlink data, and second information separated from the first information that indicates a frequency location of the resource for the ACK/NACK in response to the downlink data; sending the downlink data to the terminal; and receiving the ACK/NACK in response to the downlink data from the terminal according to the time location and the frequency location.
 2. The method according to claim 1, wherein the ACK/NACK is a first sequence or a second sequence, the first sequence represents ACK, the second sequence-represents NACK, and the first sequence and the second sequence are orthogonal to each other.
 3. The method according to claim 2, wherein the single DCI further comprises information indicating a data format for the ACK/NACK.
 4. The method according to claim 3, wherein the single DCI further comprises MCS information indicating a bit rate and a modulation scheme of the ACK/NACK.
 5. A method for transmitting downlink feedback information, performed by a terminal device, comprising: receiving single downlink control information (DCI) from a base station on a physical downlink control channel (PDCCH), wherein the single DCI includes downlink scheduling information that schedules downlink data, first information that indicates a time location of a resource for acknowledgement/negative acknowledgement (ACK/NACK) in response to the downlink data, and second information separated from the first information that indicates a frequency location of the resource for the ACK/NACK in response to the downlink data; receiving the downlink data from the base station; and sending the ACK/NACK in response to the downlink data to the base station according to the time location and the frequency location.
 6. The method according to claim 5, wherein the ACK/NACK information is a first sequence or a second sequence, the first sequence represents ACK, the second sequence represents NACK, and the first sequence and the second sequence are orthogonal to each other.
 7. The method according to claim 6, wherein the single DCI further comprises information indicating a data format for the ACK/NACK.
 8. The method according to claim 7, wherein the single DCI further comprises MCS information indicating a bit rate and a modulation scheme of the ACK/NACK.
 9. A base station, comprising: a processor; and a non-transitory storage coupled to the processor, including instructions, when executed by the processor, causing the base station to perform steps comprising: sending single downlink control information (DCI) to a terminal device on a physical downlink control channel (PDCCH), wherein the single DCI includes downlink scheduling information that schedules downlink data, first information that indicates a time location of a resource for acknowledgement/negative acknowledgement (ACK/NACK) in response to the downlink data, and second information separated from the first information that indicates a frequency location of the resource for the ACK/NACK in response to the downlink data; sending the downlink data to the terminal; and receiving the ACK/NACK in response to the downlink data from the terminal according to the time location and the frequency location.
 10. The base station according to claim 9, wherein the ACK/NACK is a first sequence or a second sequence, the first sequence represents ACK, the second sequence represents NACK, and the first sequence and the second sequence are orthogonal to each other.
 11. The base station according to claim 10, wherein the single DCI further comprises information indicating a data format for the ACK/NACK.
 12. The base station according to claim 11, wherein the single DCI further comprises MCS information indicating a bit rate and a modulation scheme of the ACK/NACK.
 13. A terminal device, comprising: a processor; and a non-transitory storage coupled to the processor, including instructions, when executed by the processor, causing the terminal device to perform steps comprising: receiving single downlink control information (DCI) from a base station on a physical downlink control channel (PDCCH), wherein the single DCI including downlink scheduling information that schedules downlink data, receiving first information that indicates a time location of a resource for acknowledgement/negative acknowledgement (ACK/NACK) in response to the downlink data, and second information separated from the first information that indicates a frequency location of the resource for the ACK/NACK in response to the downlink data; receiving the downlink data from the base station; sending the ACK/NACK in response to the downlink data to the base station according to the time location and the frequency location.
 14. The terminal device according to claim 13, wherein the ACK/NACK is a first sequence or a second sequence, the first sequence represents ACK, the second sequence represents NACK, and the first sequence and the second sequence are orthogonal to each other.
 15. The terminal device according to claim 14, wherein the single DCI further comprises information indicating a data format for the ACK/NACK.
 16. The method according to claim 15, wherein the single DCI further comprises MCS information indicating a bit rate and a modulation scheme of the ACK/NACK.
 17. A communication system, comprising: a base station, configured to: send single downlink control information (DCI) to a terminal device on a physical downlink control channel (PDCCH), wherein the single DCI includes downlink scheduling information that schedules downlink data, first information that indicates a time location of a resource for acknowledgement/negative acknowledgement (ACK/NACK) in response to the downlink data, and second information separated from the first information that indicates a frequency location of the resource for the ACK/NACK in response to the downlink data; send the downlink data to the terminal; and receive the ACK/NACK in response to the downlink data from the terminal according to the time location and the frequency location; the terminal device, configured to receive the single DCI from the base station; receive the downlink data from the base station; send the ACK/NACK in response to the downlink data to the base station according to the time location and the frequency location.
 18. The system according to claim 17, wherein the ACK/NACK is a first sequence or a second sequence, the first sequence represents ACK, the second sequence represents NACK, and the first sequence and the second sequence are orthogonal to each other.
 19. The system according to claim 18, wherein the single DCI further comprises information indicating a data format for the ACK/NACK.
 20. The system according to claim 19, wherein the single DCI further comprises MCS information indicating a bit rate and a modulation scheme of the ACK/NACK. 